Lithium ion batteries are able to store more energy than conventional batteries and are used in many portable appliances. When a lithium ion battery is being charged, lithium ions travel from the cathode to the anode. Electrons supplied at the anode reduces the lithium ions and the anode holds on to the resultant lithium, thereby storing electrical energy. When the battery is in use, the lithium discharges held electrons and lithium ions returns from the anode to the cathode.
The typical lithium battery has a graphite anode, which has a known structure comprising parallel planes of carbon between which lithium ions may enter and be stored as lithium. Such graphite anode has a specific capacity of 372 mAh/g (milli ampere×hour/gram) which is becoming hardly enough for modern day mobile gadgets. Other materials which can hold more lithium and increase the amount of energy packed into an anode has been proposed, such as aluminium, silicon and so on. However, these materials comes with different problems. For example, silicon and tin are quite unstable as anode material because of volumetric expansion, which eventually cut short the life of the battery.
It has been proposed to replace graphite in the anode with tin. Tin works in a similar way as graphite, which is to provide a structure into which the lithium can be inserted, except that it has a higher theoretical capacity of 990 mAh/g. However, tin also has a high volume expansion coefficient. A tin structure expands and contracts during lithium alloying and dealloying to the tin, and this could easily break down the structure leading to capacitance decay inside the anode.
Further proposals have been made to use tin-based material which has less volumetric expansion instead of tin. However, those tin-based materials have inferior electro-conductivity and compatibility to battery electrolyte.
Therefore, it is desirable to propose methods and apparatus with features that could mitigate these problems.